Thanks all, I might investigate those ideas.
Unfortunately, the reason I'm asking is because I bought a set of these on ebay (for a considerable amount of money), listed as excellent condition which are, of course, covered in corrosion on the outside of the blades. I wonder if there's any point in doing anything since I don't know of a way of treating the corrosion that wouldn't ruin the accuracy of the collets, which is their entire point.
Why do I never learn not to trust people on ebay?!